1. Field of the Invention
The invention relates to the surgical control of osseous hemorrhage, to the improvement of healing of osseous defects, as well as infection treatment or prophylaxis, involving orthopedic procedures utilizing materials having a putty-like consistency. More particularly, various novel, surgically implantable, absorbable, putty-like formulations, which may contain absorption accelerants, demineralized bone matrix (DBM), which is a bone growth-inducing material, and anti-infective agents to reduce the risk of postoperative infection, are used as bone hemostatic devices.
2. Description of Related Art
Cancellous and cortical bone contains relatively vascular tissues that bleed when their vasculature is disrupted. Thus, when bone is surgically incised or fractured traumatically, e.g., in open or compound fractures, there are at least two major issues which must be medically resolved. The first of these is the occurrence of osseous hemorrhage. When_osseous hemorrhage ensues, it must be stopped or effectively controlled (hemostasis) to prevent adverse surgical consequences. The second issue is that of bone growth to promote healing (osteogenesis) of the traumatized bone. Common procedures in which bone is surgically cut include open-heart surgery involving the splitting of the sternum, orthopedic and spinal surgery including hip implants, neurosurgery involving spine or cranial incisions, amputations, trauma treatment, and many other procedures.
At the present time, bone hemostasis is achieved by one or more of (i) manually impregnating the bleeding surface with commercially available, non-absorbable “bone wax”, (ii) the use of various hemostatic agents such as oxidized cellulose or microcrystalline collagen and (iii) electrocautery. None of these techniques promotes osteogenesis to any significant extent. In addition to the unmet need for an effective, rapidly absorbable bone hemostatic material, there is also a surgical need for materials to fill bone defect voids and promote healing in such cavities. A variety of paste-like materials, presently available to the surgeon for this purpose, most commonly are based upon coarsely powdered, demineralized allogeneic bone, suspended in a suitable, biocompatible vehicle. These compositions are designed for inducing osteogenesis and healing in the defect but, because their consistency, low cohesive strength, and other physical attributes of their composition, they do not reliably adhere to injured bone and are not effective hemostatic agents.
There are two major bodies of prior art concerned with bone hemostasis and with bone healing, respectively. As discussed below, up to the present time, in the main, only products based upon plasticized non-absorbable waxes have been available to the surgeon for bone hemostasis. The disadvantages of makeshift devices employing, for example, oxidized cellulose as well as the tissue-destructive use of electrocautery (discussed below) are not satisfactory alternatives.
The first body of art is directed specifically to bone waxes which are manually pressed into the pores of the bleeding bone surface, act as an effective mechanical tamponade, and prevent blood from escaping. Presently available bone waxes consist of mixtures of non-absorbable components such as bee's wax, paraffin, petrolatum, fatty ester plasticizers, and the like. These products must be warmed before use and become soft, kneadable and spreadable by the surgeon onto and into cut bone surfaces. Because available bone waxes are not absorbable and reside indefinitely where they are placed by the surgeon, they act as permanent physical barriers that inhibit osteogenesis, thereby preventing or slowing bone healing. In addition, such a site acts as a perpetual postoperative nidus for infection. If such infection does occur, it is usually chronic and difficult to treat using conventional anti-infective therapy and re-operation, to surgically excise the infected site, often becomes necessary. For these reasons, commercially available bone waxes do not enjoy widespread orthopedic use.
Other products or techniques used in this application include oxidized cellulose products indicated for soft tissue hemostasis, e.g., Surgicel®, which are absorbable and would not be expected to induce the complications cited above for bone wax. However, they are not effective hemostatic products for bone because of their inappropriate physical form (knitted fabric) and are too difficult to use effectively on cut bone because of lack of adherence within the bone pores.
The use of electrocautery, which thermally sears oozing blood vessels closed, is time-consuming and produces widespread tissue damage which may delay osteogenesis as well as allow soft tissue in-growth that interferes with normal bone union, presenting difficult problems for orthopedic surgeons in general and spine surgeons in particular.
Collagen and gelatin in various forms, alone or in combination with fibrin and suspended in various delivery vehicles have been proposed as bone hemostatic agents but problems with, for example, one or more of storage stability, cohesiveness, excessive swellability, and biocompatibility have prevented practical fruition.
The adaptation of synthetic absorbable polymers to this application has not succeeded, apparently because of technical difficulties in suitably formulating hydrolytically unstable synthetic absorbable polymers into practical products with reasonable package shelf life, useful handling properties and acceptable biocompatibility and absorption rates.
The second body of prior art primarily is concerned with bone healing and the treatment of bone defects. The bone healing prior art compilation primarily describes the development of biocompatible, absorbable vehicles to deliver and support processed particulate allogeneic bone as it is applied to defects such as excised bone cavities. These liquid or paste-like vehicles consist of a variety of polyhydroxy compounds, ester derivatives of polyols, hydrogels, and the like, sometimes containing additives to increase the viscosity of the vehicle (to retard dissipation of the vehicle and, thereby, extend the cohesiveness of the implanted mass) or factors to induce new bone growth. Anti-infective, anti-tumor and other additives also are described for these products. In no case, are these compositions indicated for, act as, or described in the art and claimed as bone hemostatic agents.